## Principal stresses and shear stress

PRINCIPAL STRESSES AND SHEAR STRESS The vertical stress intensity is not the maximum direct stress intensity within the dam section. It is therefore necessary to determine the intensity of the maximum normal stress. The maximum normal stress occurs on the major principal plane. The D/S face of the dam which is inclined at an angle α to the vertical is a principal plane, as no shear stress acts on it. If any tail water is there it contributes a pressure p’ entirely normal to the plane and is one of the principal stresses. The second principal plane will be inclined at right angles to the face of the dam and hence at an angle α to the horizontal. The stress acting on such plane is the major principal stress Pmax. All the stresses can be represented by Mohr’s circle. See Fig. 13.6. The vertical stress Pn at toe of the…